Friction materials serve in a variety of ways to control the deceleration of a variety of vehicles and machines such as, but not limited to automobiles. In an automotive vehicle, one of the purposes of the friction members is to physically stop the vehicle. These units, including disk brake pads and rotors and brake shoes and drums, convert physical movement into frictional heat. Every wheel contains either a disk or brake drum assembly.
Friction members for brakes are typically made from materials that will produce friction with the rotor or drum and withstand the high temperatures developed during braking. One of the most common type of friction materials used in brakes and clutches for normal duty is generally termed organic. These organic friction materials usually contain about 30–40 weight % of organic components. One of the main constituents of practically all organic friction materials at one time was asbestos fiber, although small quantities of other fibrous reinforcement may have been used. Since asbestos alone did not offer all of the desired properties, other materials called property modifiers, either abrasive or nonabrasive, were added to provide desired amounts of friction, wear, fade, recovery, noise, and rotor compatibility. A resin binder, such as phenolic or cresylic resin, held the other materials together in a matrix. This binder was not completely inert and made contributions to the frictional characteristics of the composite. Because asbestos has been alleged to be the cause of certain health problems and is no longer environmentally acceptable, most modern brake pads and drum linings are made without asbestos. Thus, most current friction linings are made from synthetic and steel fibers, and iron, ceramic, and metallic powders.
Conventional friction materials operate under a whole range of operating temperatures and pressures. However, the wear mechanisms governing the wear life of friction materials under low-duty conditions are significantly different from the factors governing heavy-duty conditions. During use, the physicochemical changes at the interface between the friction material and cast iron drums, for example, govern the performance behavior of the friction couple. The choice of the proper abrasive has a great bearing on the formation and destruction of the dynamic friction (i.e., transfer) film. Unfortunately, conventional friction material compositions are somewhat unsatisfactory with respect to the performance behavior of the friction couple, especially during low-duty conditions. This can lead to sub-par performance of the braking system, as well as objectionable noises when braking, both of which lead to consumer dissatisfaction.
Therefore, there exists a need for a friction material composition having improved abrasive characteristics to enhance the performance behavior of the friction couple, especially during low-duty conditions.